Conditions & Treatments

Substance Abuse / Chemical Dependency

There are three different terms used to define substance-related disorders, including substance abuse, substance dependence, and chemical dependence.

Substance Abuse/Chemical Dependency

What is substance abuse/chemical dependence?

The main words used medically to describe substance abuse or addiction include the following:

Substance (drug) abuse (alcohol or other drugs)

Substance abuse is the medical term used to describe a pattern of substance (drug) use that causes significant problems or distress, such as failure to attend work or school, substance use in dangerous situations (driving a car), substance-related legal problems, or continued substance use that interferes with friendships and/or family relationships. Substance abuse, as a recognized medical brain disorder, refers to the abuse of illegal (such as marijuana, heroin, cocaine, or methamphetamine)or legal substances (such as alcohol, nicotine, or prescription drugs). Alcohol is the most common legal drug of abuse.

Substance (drug) dependence

Substance dependence is the medical term used to describe abuse of drugs or alcohol that continues, even when significant problems related to their use have developed. Signs of dependence include:

  • Tolerance to or need for increased amounts of the drug to get an effect

  • Withdrawal symptoms that happen if you decrease or stop using the drug that you find difficult to cut down or quit

  • Spending a lot of time to obtain, use, and recover from the effects of using drugs

  • Withdrawal from social and recreational activities

  • Continued use of the drug even though you are aware of the physical, psychological, and family or social problems that are caused by your ongoing drug abuse

What substances are most often abused?

Substances frequently abused include, but are not limited to, the following:

  • Alcohol

  • Marijuana

  • Tobacco

  • Prescription drugs, such as pain pills, stimulants, or anxiety pills 

  • Methamphetamine  

  • Cocaine

  • Opiates

  • Anabolic steroids

  • Hallucinogens 

  • Inhalants

What causes drug abuse or dependence?

Cultural and societal factors determine what are acceptable or allowable forms of  drug or alcohol use. Public laws determine what kind of drug use is legal or illegal. The question of what type of substance use can be considered normal or acceptable remains controversial. These medical disorders, substance abuse and dependence, are caused by multiple factors including genetic vulnerability, environmental stressors, social pressures, individual personality characteristics, and psychiatric problems. However, which of these factors has the biggest influence in any one person cannot be determined in all cases.

What are the symptoms of drug abuse or dependence?

The following are the most common behaviors that indicate an individual is having a problem with drug or alcohol abuse. However, each individual may experience symptoms differently. Symptoms may include:

  • Getting high on drugs or getting intoxicated (drunk) on a regular basis

  • Lying, especially about how much they are using or drinking

  • Avoiding friends and family members

  • Giving up activities they used to enjoy, such as sports or spending time with nonusing friends

  • Talking a lot about using drugs or alcohol

  • Believing they need to use or drink in order to have fun

  • Pressuring others to use or drink

  • Getting in trouble with the law

  • Taking risks, such as sexual risks or driving under the influence of a substance

  • Work performance suffers due to substance abuse before, after, or during working or business hours

  • Missing work due to substance use

  • Depressed, hopeless, or suicidal feelings

The symptoms of drug or alcohol abuse may resemble other medical problems or psychiatric conditions. Always consult your doctor for a diagnosis.

How is drug abuse or dependence diagnosed?

A family doctor, psychiatrist, or qualified mental health professional usually diagnoses substance abuse. Clinical findings often depend on the substance abused, the frequency of use, and the length of time since last used, and may include the following:

  • Weight loss

  • Constant fatigue

  • Red eyes

  • Little concern for hygiene

  • Laboratory abnormalities

  • Unexpected abnormalities in heart rate or blood pressure

  • Depression, anxiety, or sleep problems 

Treatment for drug abuse or dependence

Specific treatment for drug abuse or dependence will be determined by your doctor based on:

  • Your age, overall health, and medical history

  • Extent of the symptoms

  • Extent of the dependence

  • Type of substance abused

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

A variety of treatment (or recovery) programs for substance abuse are available on an inpatient or outpatient basis. Programs considered are usually based on the type of substance abused. Detoxification (if needed, based on the substance abused) and long-term follow-up management or recovery-oriented systems of care are important features of successful treatment. Long-term follow-up management usually includes formalized group meetings and psychosocial support systems, as well as continued medical supervision. Individual and family psychotherapy are often recommended to address the issues that may have contributed to and resulted from the development of a substance abuse disorder.

Treatment Programs


Massachusetts General Hospital understands that a variety of factors influence patients' health care decisions. That's just one reason why we're dedicated to ensuring patients understand their diagnosis and treatment options. Because a single option might not serve all patients, we offer a wide range of coordinated treatments and related services across the hospital. Patients should consult with their primary care doctor or other qualified health care provider for medical advice and diagnosis information.

Select a treatment program for more information:



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